CLD Interior Lighting 4 — Questions and Answers
Question 1: A designer wants to create visual interest on a rough stone wall using grazing light. The fixture should be positioned:
- Far from the wall, angled at 45°
- Directly overhead, aimed straight down
- Very close to the wall surface, nearly parallel to it (Correct answer)
- Behind the viewer, aimed at the wall center
Correct answer: Very close to the wall surface, nearly parallel to it
Grazing light placed very close to and nearly parallel to a textured surface emphasizes surface relief by casting dramatic shadows across irregularities.
Question 2: Which ASHRAE/IES standard is most directly applicable to interior lighting energy compliance for new commercial buildings in the US?
- ASHRAE 90.1 (Correct answer)
- ASHRAE 55
- ASHRAE 62.1
- ASHRAE 189.1
Correct answer: ASHRAE 90.1
ASHRAE 90.1 (Energy Standard for Buildings) sets the Lighting Power Density (LPD) limits and control requirements that govern energy-compliant interior lighting design in commercial construction.
Question 3: A retail clothing store wants to make merchandise appear most vibrant. Which lamp specification is most appropriate?
- CRI 70, 4000K
- CRI 90+, 3000K (Correct answer)
- CRI 60, 5000K
- CRI 80, 2700K
Correct answer: CRI 90+, 3000K
High CRI (90+) at a warm 3000K enhances color saturation and rendering accuracy of fabrics, making merchandise appear vibrant and appealing.
Question 4: When calculating average illuminance using the Lumen Method (zonal cavity method), which factor accounts for dirt accumulation and lamp lumen depreciation over time?
- Coefficient of Utilization (CU)
- Light Loss Factor (LLF) (Correct answer)
- Room Cavity Ratio (RCR)
- Spacing Criterion (SC)
Correct answer: Light Loss Factor (LLF)
The Light Loss Factor (LLF) is a composite multiplier that accounts for lamp lumen depreciation, luminaire dirt depreciation, and other factors reducing maintained illuminance over time.
Question 5: In a conference room with video conferencing capabilities, what is a key lighting design concern for the camera-facing wall?
- Providing at least 200 fc of ambient light behind participants
- Avoiding bright windows or high-luminance backgrounds that cause silhouetting (Correct answer)
- Using only cool-white 6500K sources for accurate color on screen
- Eliminating all shadows on participants' faces
Correct answer: Avoiding bright windows or high-luminance backgrounds that cause silhouetting
Bright backgrounds or windows behind participants create silhouetting on camera; the designer must control luminance ratios to keep faces well-exposed relative to the background.
Question 6: What is the purpose of specifying a 'visual comfort probability (VCP)' value for a luminaire?
- To predict energy savings over a fluorescent baseline
- To quantify the percentage of observers who would find a luminaire's glare acceptable (Correct answer)
- To measure the fixture's thermal performance under load
- To rate the fixture's resistance to vibration
Correct answer: To quantify the percentage of observers who would find a luminaire's glare acceptable
VCP expresses the percentage of people, positioned at the least favorable location, who would judge the luminaire's direct glare as acceptable for the given installation.
Question 7: Which lighting application technique uses a large-aperture luminaire or softbox positioned close to a subject to produce soft, wraparound illumination with minimal harsh shadows?
- Spotlighting
- Grazing
- Diffuse area lighting (Correct answer)
- Collimated beam projection
Correct answer: Diffuse area lighting
Diffuse area lighting from a large source close to the subject produces soft-edged shadows and even illumination because light wraps around the subject from many angles.
CLD Interior Lighting 4
A designer wants to create visual interest on a rough stone wall using grazing light.
The fixture should be positioned: